It may be purely anatomical, standing upright, the skull base must be
changed and that may allow some favourable changes. For example, enlargement
of the hypoglossal canal, the route for the nerves that innervate the throat
region. (We easily under-estimate how complex swallowing etc is, it is a
problem with some brain pathologies.) You might want to look up the "social
chess" theory of human evolution, the idea being that what drove
encephalisation was the need to explain what remains the most complex known
thing in the universe: human behavior. We had to develop an "allocentric"
capacity: to understand the motives of others and their probable future
behavior. So the story goes. It makes a certain sense because a single human
being is the most helpless of creatures and and if you can't get on with
other people you're doomed.
Have a look at Terrance Deacon's "The Symbolic Species", he has some
interesting things to say about hominin encephalisation though not directly
related to the above argument.
.
"rAgAv" <ragav.payne from googlemail.com> wrote in message
news:1184469559.678291.133340 from o11g2000prd.googlegroups.com...
> Hello,
>> I've been wondering why human beings alone have that big, unique and
> complex cortex. Can you help me with your views?
>> --
> rAgAv
>